fix: Fix setting the locale

[marien-probesys]

Related issue(s)

Two problems happened. First, the Accept-Language header was ignored when the user wasn't logged-in. It means that the French locale was always used. The refactor of the LocaleSubscriber fixes this.

The second problem was that once the session expired, but that the user was logged in again through the "remember me" cookie, the locale wasn't set anymore. This is why I introduce a UserLocaleSubscriber which is triggered on "interactive login", meaning it is called both on normal login, and on "remember me" login.

How to test manually

1. In the preference of your browser, put the English (en) as your preferred language
2. On login, check that the page is translated in English
3. Do the same with French (fr)
4. Once logged-in (with remember me checked), choose the English as default language
5. Remove the PHPSESSID cookie
6. Refresh the page and check that it's still translated in English

Reviewer checklist

• Code is manually tested
• Interface works on both mobiles and big screens
• Interface works on both Firefox and Chrome
• Tests are up to date
• Documentation is up to date
• Pull request has been reviewed and approved